Field of the Invention
The present invention relates to a fixing apparatus and an image forming apparatus.
Description of the Related Art
As a known art in a fixing apparatus, there is a control method (wave number control) of generating an application pattern by appropriately selecting a half wave of an AC waveform as a drive power for a heater and supplying the generated application pattern to the heater as drive power (refer to JP 2013-222097 A).
For example, the temperature of the heater can be properly controlled by appropriately controlling the number of half waves supplied in a predetermined cycle, namely, a duty ratio of the application pattern, corresponding to the magnitude of the drive power to be supplied.
Meanwhile, there is a disclosed image forming apparatus that performs phase control, specifically, supplies the drive power to the heater by turning on a switching element on a certain phase angle within a half wave of the AC waveform in order to suppress fluctuation, namely, flickering of an illumination apparatus (refer to JP 2013-222097 A).
It would be true that the wave number control on the image forming apparatus described in JP 2013-222097 A would cause no problem in a case where the drive power with a high duty ratio on the application pattern is supplied to the heater. Unfortunately, however, in a case where the drive power with a low duty ratio on the application pattern is supplied to the heater, an interval between the half waves of the AC waveform might increase and lower the heater temperature in a period when the half wave of the AC waveform is not supplied. This would cause, in a case where the half wave of the AC waveform half is supplied again, generation of inrush current in the heater and lead to generation of flickering.